Tuesday, August 31, 2010

The basic circuit illuminates up to ten LEDs in sequence, following the rhythm of music or speech picked-up by a small microphone. The expanded version can drive up to ten strips, formed by up to five LEDs each, at 9V supply.

Skema Rangkaian Dancing LEDs

IC1A amplifies about 100 times the audio signal picked-up by the microphone and drives IC1B acting as peak-voltage detector. Its output peaks are synchronous with the peaks of the input signal and clock IC2, a ring decade counter capable of driving up to ten LEDs in sequence.An additional circuit allows the driving of up to ten strips, made up by five LEDs each (max.), at 9V supply. It is formed by a 10mA constant current source (Q1 & Q2) common to all LED strips and by a switching transistor (Q3), driving a strip obtained from 2 to 5 series-connected LEDs. Therefore one transistor and its Base resistor are required to drive each of the strips used.

List Component of Dancing LEDs Circuit

R1: 10K 1/4W Resistor

R2,R3: 47K 1/4W Resistors

R4: 1K 1/4W Resistor

R5,R6,R7: 100K 1/4W Resistors

R8: 820R 1/4W Resistor

C1,C3: 100nF/63V Ceramic or Polyester Capacitors

C2: 10µF/50V Electrolytic Capacitor

C4: 330nF/63V Polyester Capacitor

C5: 100µF/25V Electrolytic Capacitor

D1: 1N4148

D2-D11: LEDs (any type and color)

IC1: LM358

IC2: 4017

M1: electret microphone

SW1: SPST Switch

B1: 9V PP3 Battery

Additional circuit parts:

R9,R10: 10K 1/4W Resistors

R11: 56R 1/4W Resistor

D12,D13 etc.: LEDs (any type and color)

Q1,Q2: BC327

Q3: BC337

Note:

The sensitivity of the circuit can be varied changing R4 value.

C4 value can be varied from 220 to 470nF in order to change the circuit speed-response to music peaks.

Adopting the additional circuit, only one item for R10, R11, Q1 and Q2 is required to drive up to ten LED strips. On the contrary, one item of R9 and Q3 is necessary to drive each of the strips you decided to use.

Each R9 input must be connected to IC2 output pins, in place of the LEDs D2-D11 shown. R8 must also be omitted.

Whishing to use a lower number of LEDs or LED strips, pin #15 of IC2 must be disconnected from ground and connected to the first unused output pin.

For example: if you decided to use 5 LEDs, pin #15 of IC2 must be connected to pin #1; if you decided to use 8 LEDs, pin #15 of IC2 must be connected to pin #9 etc.

Current drawing of the circuit is about 10mA.

Whishing to use a wall-plug adapter instead of a 9V battery, you can supply the circuit at 12V, allowing the use of up to 6 LEDs per strip, or at 15V, allowing the use of up to 7 LEDs per strip.